U.S. Pat. No. 3,923,636, Mead et al., Dec. 2, 1975, discloses the preparation of lube oils of improved viscosity index by hydrocracking a heavy oil charge stock. The aromatics are recovered from a heavy cut by solvent extraction; an optional solvent dewaxing step is disclosed.
U.S. Pat. No. 4,162,962, Stangeland, July 31, 1979, discloses a sequential hydrocracking and hydrogenation process for the production of UV stable lube oils.
U.S. Pat. No. 3,962,071, Ito et al., June 8, 1976, discloses a process for producing lubricating oils of greater stability by hydrogenating the lubricating oil fraction of a hydrocrackate in the presence of a palladium catalyst supported on a silica-containing refractory aluminum oxide carrier.
U.S. Pat. No. 3,876,522, Campbell et al., Apr. 8, 1975, discloses a process comprising hydrocracking an oil boiling above 650.degree. F., fractionating the hydrocrackate into two lubricating oil fractions, and hydrogenating each of the two fractions.
U.S. Pat. Nos. 3,852,207, Stangeland et al., Dec. 3, 1974, 3,790,470, Mead et al., Feb. 5, 1974, and 3,666,657, Thompson et al., May 30, 1972, disclose improving the quality of hydrocracked oils by a subsequent hydrogenation step.
U.S. Pat. No. 4,181,598, Gillespie et al., Jan. 1, 1980, discloses the preparation of a lube base stock oil of improved pour point and stability from waxy crude oil fractions by solvent refining, catalytic dewaxing over a ZSM-5 zeolite catalyst, and hydrotreating.
U.S. Pat. No. 4,181,597, Yan et al., Jan. 1, 1980, discloses a process for improving the photolytic and thermal stability of a hydrocracked stock to thermal and photolytic oxidation by chemical reaction of the oil with stabilizing agents, such as olefins, alcohols, esters, and alkylhalides.
U.S. Pat. No. 4,176,050, Chen et al., Nov. 27, 1979, discloses the preparation of lubricating oils from waxy distillate lubricating stocks by solvent refining followed by catalytic dewaxing.
U.S. Pat. No. 3,755,145, Argauer, Aug. 28, 1973, discloses a process for preparing low pour point lube oils by hydrocracking a lube oil stock using a catalyst mixture comprising a conventional cracking catalyst and ZSM-5.
U.S. Pat. No. Re. 28,398, Chen et al., Apr. 22, 1975, (of U.S. Pat. No. 3,700,585), discloses dewaxing petroleum charge stocks using ZSM-5-type zeolites.
U.S. Pat. No. 4,171,257, O'Rear et al., Oct. 13, 1979, discloses the preparation of olefins from hydrocarbons using a low pressure ZSM-5 reactor and a low nitrogen feed.